Two-part polyurethane is a technology which can be applied to a variety of applications. Two-part polyurethane compositions in which one part comprises polyol(s) and the second part comprises polyisocyanate(s) can be employed. As polyols a wide range of molecules can be employed, such as polyether polyols, polyester polyols and acrylic polyols. These two-part polyurethanes are fast curing. Furthermore, they have a short pot-life, which can be problematic for certain applications, for example, for applications of a larger area of application. Furthermore, they can have a rather high viscosity after mixing. In order to reduce the viscosity, additional solvent can be used. However, this contravenes the trend of more stringent regulations in the market concerning a reduction of solvents or VOC (Volatile Organic Compounds) which is based on ecological and ecotoxic reasons.
Hyperbranched polymers are a recently found class of polymers and can be obtained from different monomers having unsaturated C—C bonds. Hyperbranched polymers have a different structure than traditional polymers, for example, polyols, which are either linear or only slightly branched. Hyperbranched polymers exhibit a branched structure. Hyperbranched polymers can be made through one-pot synthesis and therefore can be cost effective.
U.S. Pat. No. 4,880,889 discloses a preparation of hydroxyl functional acrylic polymer with monomers having more than one C—C double bond using a mercapto compound as chain stopper, being effectively a chain transfer agent for the radical polymerization process.
U.S. Pat. No. 5,767,211 discloses the preparation of (meth)acrylate functional hyperbranched polymers used for photopolymerization using a cobalt (II) complex as chain transfer catalyst.
International Publication No. WO 98/04603 A1 discloses a thermoformable cast being directly formed by the polymerization of different (meth)acrylic monomers in the presence of cobalt (II) complexes, for example, of a bis(borondifluoro-dimethylglyoximate) cobaltate (II) complex.
The preparation of cobalt (II) complexes, for example, of cobalt (II) oxime complexes, and their use as chain transfer catalysts for free radical polymerization are disclosed in U.S. Pat. No. 4,694,054, A. Bakac et al., J. Am. Chem. Soc. 1984, 106, 5197-5202 and A. Bakac et al., J. Am. Chem. Soc. 2002, 124, 5616-5617.
U.S. Pat. No. 5,115,064 discloses isocycanate functional acrylic copolymers being prepared from the free radical polymerization of isocyanatoalkyl esters of (meth)acrylic acid in the presence of mercapto compounds as regulators, which then in a second step may be crosslinked by polyols.